Size Dependence of Charge-Density-Wave Orders in Single-Layer NbSe2 Hetero/Homophase Junctions.

Controlling charge-density-wave (CDW) orders in two-dimensional (2D) crystals has attracted a great deal of interest because of their fundamental physics and their demand inse in miniaturized devices. In this work, we systematically studied the size-dependent CDW orders in single-layer hetero/homo-NbSe2 stacking junctions. We found that the CDW orders in the top 1T-NbSe2 layer of the junctions are highly dependent on its lateral size. For the 1T/2H-NbSe2 heterojunction, the critical lateral size of 1T-NbSe2 islands for the formation of well-defined CDW orders is ∼26 nm, whereas below 15 nm, the CDW orders melt. However, for the 1T/1T-NbSe2 homojunction, the CDW orders in the islands can persist even with a lateral size of <11 nm. Our findings illuminate the fresh phenomenon of size-dependent CDW orders existing in 2D van der Waals hetero/homojunctions and provide useful information for the control of CDW orders.

Impacts of COVID-19 on tourists' destination preferences: Evidence from China.

Using data of online ticket sales for attractions in the seven provinces of South Central China, this study focuses on the impact of COVID-19 on tourists' destination preferences after the end of lockdown. Empirical results reveal that tourists' destination preferences have changed significantly, which holds under a number of robustness checks. Specifically, we find that tourists avoid traveling to destinations with more confirmed cases of COVID-19 relative to their places of origin, especially Hubei Province, and prefer destinations close to home, especially local attractions. The empirical findings have significant implications for managers and policymakers in tourism and we provide potential mechanisms for these findings based on signaling, risk perception, and prospect theory.

Visualizing Spatial Evolution of Electron-Correlated Interface in Two-Dimensional Heterostructures.

Microscopically visualizing the evolution of electronic structures at the interface between two electron-correlated domains shows fundamental importance in both material science and physics. Here, we report scanning tunneling microscopy and spectroscopy studies of the interfacial electronic structures evolution in a phase-engineered monolayer NbSe2 heterostructure. The H-NbSe2 metallic state penetrates the Mott insulating T-NbSe2 at the H/T phase interface, with a prominent 2D charge density wave (CDW) proximity effect. Moreover, an insulating Mott gap collapse with the disappearance of the upper Hubbard band is detected at the electronic phase transition region. Theoretical calculations reveal that such insulating Mott gap collapse can be attributed to the electron doping effect induced by the interface. Our findings promote a microscopical understanding of the interactions between different electron-correlated systems and provide an effective method for controlling the Mott insulating states with phase engineering.

Tuning Molecular Superlattice by Charge-Density-Wave Patterns in Two-Dimensional Monolayer Crystals.

Charge density wave (CDW) in two-dimensional (2D) crystals plays a vital role in tuning the interface structures and properties. However, how the CDW tunes the self-assembled molecular superlattice still remains unclear. In this study, we investigated the self-assembled manganese phthalocyanine (MnPc) molecular superlattice on single-layered 1T- and 2H-NbSe2 crystals under regulation by distinct CDW patterns. We observe that, in low coverage, MnPc molecules preferentially adsorb on 2H-NbSe2 compared to 1T-NbSe2. With increasing coverage, MnPc can form a highly ordered superlattice on 2H-NbSe2; however, it is randomly distributed on 1T-NbSe2. We reveal a perfect geometric commensurability between the molecular superlattice and intrinsic CDW pattern in 2H-NbSe2 and a poor commensurability for that of 1T-NbSe2. We believe that the subtly different geometric commensurability dominates the different adsorption and arrangement of the molecular superlattices on 2D CDW patterns. Our study provides a pioneering approach for tuning the molecular superlattices using the CDW patterns.

Expression and prognostic significance of miR-375 and miR-221 in liver cancer.

The purpose of this study was to investigate the expression of miR-375 and miR-221 in liver cancer, and examine the correlations with pathological parameters and prognosis. We collected tumors and tumor-adjacent normal tissue from 70 patients with liver cancer admitted to the Department of General Surgery of Zhejiang Hospital. The expression of miR-375 by RT-qPCR was significantly lower in liver cancer tissues than that in the tumor-adjacent normal tissues, and the low expression was correlated with the lymphatic metastasis and TNM stage. By contrast, the expression of miR-221 was significantly higher in liver cancer than that in the tumor-adjacent tissues, and the high expression was correlated with the lymphatic metastasis and TNM stage. The overall 5-year survival rate of patients was 12.9% (9/70). Single-factor survival analysis revealed that miR-375 and miR-221 were the factors affecting the overall survival rate of liver cancer (P<0.05) and multivariate survival analysis by Cox proportional hazards model showed that miR-375 and miR-221 were the independent factors affecting the survival time of patients with liver cancer. Low expression of miR-375 and high expression of miR-221 are closely correlated with the occurrence and development of liver cancer, especially lymphatic metastasis and TNM stage. Thus, miR-375 and miR-221 can serve as reference biomarkers for guiding the treatment of liver cancer and for estimating prognosis.

Effects of naringin on the expression of miR-19b and cell apoptosis in human hepatocellular carcinoma.

The effects of naringin on the expression of miR-19b and cell apoptosis were investigated in the human hepatocellular carcinoma cell line HepG2. HepG2 cells were treated with varied concentrations of naringin. The effects of naringin on the proliferation of HepG2 cells were observed by an MTT assay, morphological changes of cells were observed by an inverted microscope, cell apoptosis was detected by DAPI staining, miR-19b mRNA levels were determined with RT-PCR, and the expression of Bax and Bcl-2 proteins was examined by western blot assay. MTT results showed that naringin significantly inhibited the proliferation of HepG2 cells. Apoptotic HepG2 cells showed obvious changes in morphology under inverted microscope. DAPI staining suggested that naringin could induce cell shrinkage and nuclear chromatin condensation. RT-PCR results showed that naringin could upregulate the expression of miR-19b mRNA. Finally, western blot suggested that naringin upregulated the expression of Bax protein, but downregulated the expression of Bcl-2 protein. In conclusion, naringin can upregulate the expression of miR-19b mRNA and induce HepG2 cell apoptosis. In addition, it can also upregulate the expression of Bax protein and downregulate the expression of Bcl-2 protein during the process of apoptosis.